Stock-Based Compensation (Summary Of SAR Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Stock Appreciation Rights [Roll Forward]
Outstanding, Shares	1,112,382	1,179,286
Granted, Shares	168,716
Forfeited, Shares	(8,856)
Expired, Shares	(276)
Exercised, Shares	(226,488)
Outstanding, Weighted Average Exercise Price, Beginning Balance	$ 37.13
Granted, Weighted Average Exercise Price	58.42
Forfeited, Weighted Average Exercise Price	46.86
Expired, Weighted Average Exercise Price	43.52
Exercised, Weighted Average Exercise Price	29.82
Outstanding, Weighted Average Exercise Price, Ending Balance	$ 41.77
Outstanding, Weighted Average Remaining Contractual Term (in years)	7 years 1 month
Outstanding, Aggregate Intrinsic Value, Ending Balance	$ 25,584